The present invention relates to a projector type vehicle headlamp and more particularly to a vehicle headlamp having a movable shade.
In general, projector type vehicle headlamps are constructed such that a projection lens is disposed on an optical axis which extends in a longitudinal direction of a vehicle and a light source is disposed rearward of a rear focal point of the projection lens, whereby light from the light source is reflected by a reflector so as to converge towards the optical axis. In order to form a low beam light distribution pattern by the projector type vehicle headlamp, the reflected light from the reflector is partially shielded by a shade which is disposed such that an upper edge thereof is situated in the vicinity of the optical axis near the rear focal point of the projection lens, so that a predetermined cut-off line is formed at an upper end portion a low beam light distribution pattern.
In the above projector type vehicle headlamps, JP-A-2003-257218 discloses a projector type vehicle headlamp having, as the shade, a movable shade which is made to move to a light shielding moderating position where a shielding amount of the reflected light shielded by the shade is reduced.
In addition, JP-U-02-047704 and JP-A-2001-229715 disclose projector type vehicle headlamps in which a light source is made up of a light emitting portion of a light source bulb which is inserted into a reflector from a side of an optical axis so as to be fixed in place therein. That is, a so-called sideways insertion type lamp construction.
In the vehicle headlamp described in JP-A-2003-257218, since a high beam light distribution pattern can be formed by moving the movable shade to the light shielding moderating position, the single lamp can be used both for low beam and highbeam. In the vehicle headlamp described JP-A-2003-257218, however, since the light source bulb is inserted into the reflector from the rear thereof on the optical axis so as to be fixed in place therein, the longitudinal length of the headlamp becomes long and this makes it difficult to secure a space where the headlamp is assembled in a vehicle.
To cope with this, in case a sideways insertion type lamp construction such as described in JP-U-02-047704 and JP-A-2001-229715 is adopted in the projector type vehicle headlamp having the movable shade, the longitudinal length of the headlamp can be shortened, thereby making it possible to attempt to make the headlamp compact.
In the vehicle headlamps described in JP-U-02-047704 and JP-A-2001-229715, however, since the light source bulb is inserted into the reflector so as to be fixed in place therein on the same horizontal plane as that of the optical axis, the following problem emerges.
Namely, the projector type vehicle headlamp is suitable for forming a diverging area of the light distribution pattern, however, since a light source bulb inserting and fixing hole is formed in an optical axis sideways area when the light source bulb is inserted into the reflector so as to be fixed in place therein on the same horizontal plane as that of the optical axis, the relevant optical axis sideways area cannot be used effectively to control the light distribution. Thereby, there is caused a problem that sufficient brightness cannot be ensured for the diverging area of the light distribution pattern.